<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>

    <script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>
</head>
<body>
    <div id="app">

        <input type="text" v-model="n1">
        <select v-model="opt">
            <option value="+">+</option>
            <option value="-">-</option>
            <option value="*">*</option>
            <option value="/">/</option>
        </select>

        <input type="text" v-model="n2">

        <input type="button" value="=" @click="calc">


        <input type="text" v-model="result">
    </div>
    <script>
        // 创建Vue实例，
        var vm = new Vue({
            el: '#app',
            data: {
                n1: 0,
                n2: 0,
                result: 0,
                opt: '+'
            },
            methods: {
                calc(){ //计算方法
                    // switch(this.opt){
                    //     case '+':
                    //         this.result = parseInt(this.n1) + parseInt(this.n2)
                    //         break;
                    //     case '-':
                    //         this.result = parseInt(this.n1) - parseInt(this.n2)
                    //         break;
                    //     case '*':
                    //         this.result = parseInt(this.n1) * parseInt(this.n2)
                    //         break;
                    //     case '/':
                    //         this.result = parseInt(this.n1) / parseInt(this.n2)
                    //         break;
                    // }

                    // 这种方式尽量少用
                    var codeStr = 'parseInt(this.n1)' + this.opt + 'parseInt(this.n2)'
                    this.result = eval(codeStr)
                }
            }
        });
    </script>
</body>
</html>